Cheap dark sunglasses without UV protection are worse for your eyes than no sunglasses at all. The dark lens makes your pupils dilate; the missing UV filter then lets more UV reach the retina than would have without the glasses on. Here's why UV400 is the threshold.
The two UV bands that matter
Solar ultraviolet light comes in three bands: UVA (315-400nm), UVB (280-315nm), and UVC (100-280nm). UVC is absorbed entirely by the atmosphere — only UVA and UVB reach Earth's surface in significant amounts. Both can damage the eye, but they damage different structures.
UVB causes acute corneal damage (photokeratitis — essentially a sunburn on the cornea, painful within hours of exposure). UVA causes long-term retinal and lens damage that accumulates across decades — the primary contributors to age-related macular degeneration and cataracts. The American Academy of Ophthalmology estimates that 10-20% of cataracts are UV-induced rather than purely age-related.
Why 400 nanometers is the threshold
The UV400 designation means a lens blocks 99-100% of UV light up to 400 nanometers — which is the upper boundary of UVA. Lenses rated only for UV380 or UV395 leave a gap between their blocked range and the full UVA spectrum, allowing some long-wavelength UVA through.
The 400nm number isn't arbitrary. It's the cumulative threshold the World Health Organization, American Optometric Association, and FDA all use as the minimum for 'full UV protection' in eyewear. Below 400nm, the protection is partial.
Why dark cheap sunglasses can be worse than no sunglasses
When you put on dark sunglasses, your iris dilates the pupil to let more light in (the brain compensates for the darker visual field). This is reflexive and happens within seconds. If the dark sunglasses lack UV protection, the dilated pupil now lets MORE UV reach the retina than it would have without sunglasses on (where the brighter ambient light would have kept the pupil constricted).
Pediatric ophthalmology research has documented elevated retinal-damage risk in children wearing fashion sunglasses without UV protection at the beach, particularly during the high-UV midday hours. The advisory from most medical organizations: if sunglasses don't have a verified UV rating, don't wear them — sun-squinting is safer than non-UV-protected darkness.
How to verify UV400
Reputable brands print 'UV400' or '99-100% UV Protection' directly on the product page or hangtag. Look for one of these specific phrasings: 'UV400,' 'UVA + UVB Protection,' '100% UV Protection,' or the CE category number (any CE 2, 3, or 4 rating includes full UV protection in EU markets).
If you have existing sunglasses without a clear UV rating, take them to any optometrist's office for free testing — most offices have a UV-meter that will tell you exactly what percentage of UV the lens blocks. Most optometrists do this as a free walk-in service.
OHO's prints UV400 on every product page, and the brand sources its lenses from a single Italian polarization-and-UV-coating supplier (Carl Zeiss Vision optical-coating partners) used across the catalog. Every pair meets the UV400 threshold.
Shop the coastal line
Coastal-named UV400-rated everyday sunglasses.
Sources & citations
- World Health Organization. "Sun Protection: Eyes." who.int
- American Academy of Ophthalmology. "UV Protection and Sunglasses." aao.org
- American Optometric Association. "Statement on UV Protection in Eyewear." aoa.org
- FDA Center for Devices and Radiological Health. "Sunglasses Regulation 21 CFR 880.6700." fda.gov
All coastal
The full OHO's lineup at Curated Sense — polarized UV400-rated across every silhouette.
All coastal →Frequently asked
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